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A partial rendering of the City of Grand Rapids' biodigester. Courtesy City of Grand Rapids

Grand Rapids has begun building a $38-million biodigester that will convert food waste into energy.

City officials and business leaders gathered for a groundbreaking ceremony last week at the city’s Environmental Services Department’s Water Resource Recovery Facility, or WRRF, at 1300 Market Ave. SW.

A new $38-million waste-to-energy biodigester and related sludge treatment system is being built at the site.

The project, initially projected to be completed in 2018, is now estimated to be done by 2019.

Grand Rapids Mayor Rosalynn Bliss said the biodigester is part of the city’s goal of using 100-percent renewable energy to power city buildings by 2025.

“This project demonstrates the overwhelming public and private support we have in our region for green infrastructure,” Bliss said.

The city generates almost 30 percent of its electricity from renewable energy.

Why it’s needed

Environmental Services Director Mike Lunn said when the project was announced in February that the system is the city’s chosen solution for treating the growing stream of food waste from companies such as Founders Brewing Co., Coca-Cola and Amway.

City Manager Greg Sundstrom added it was the most sustainable and financially sound option on the table.

“Without this biodigester, Grand Rapids would exceed the capacity of our current system within the next few years and that would require spending $120 million to expand waste treatment operations at the city’s Water Resource Recovery Facility,” Sundstrom said. “Our plan reduces costs, protects the environment in a sustainable manner and advances progress on our city’s important quality-of-life priorities.”

How it works

Biodigesters are concrete chambers that mimic the work done by fermenters in a brewery, converting carbon to carbon dioxide and methane, Public Services Managing Director Tom Almonte said.

The plan will be to take organic waste and combine it with microorganisms in three sealed, air-tight tanks that each have a capacity of 1.4-million gallons. The project also provides space for an expansion of three additional tanks at the site to allow existing or future high-strength waste customers to tap into the system.

Water from a new $4-million, 10-inch transmission pipe the city has installed underneath Market Avenue will carry concentrated food waste from Founders Brewing and other businesses, such as SET Environmental, to the city’s treatment plant.

The waste will then be recycled through the biodigester to create a biogas that produces energy, primarily electricity, that can then be used to power and heat the buildings and operations at WRRF and to operate the digesters, Almonte said.

“Carbon filters and other technologies will be used to control the smell,” Lunn said. “It’s based on the same system we use at the wastewater treatment facility to control odors from raw solid waste.”

Funding

Grand Rapids will pay for the project with tax-exempt municipal bonds. Electricity production from the biodigester will help offset the costs of the investment, which is expected to help keep consumers’ rates steady, Deputy City Manager Eric DeLong said.

The biodigester system will produce about 95 percent of the WRRF electricity needs, DeLong said.

When fully operational, the biodigester system might open the door to potential new revenue streams, Commissioner Ruth Kelly said. The sale of city-generated phosphorous recovery has a potential annual return on investment that will make the investment revenue neutral to positive.

Firms on the project

Pasadena, California-based Tetra Tech is leading the design phase of the biodigester installation.

According to the city, the biodigester project has potential long-term benefits across Kent County, because the WRRF goes beyond serving the Grand Rapids to include the communities of Walker, Kentwood, Cascade Township, Grand Rapids Township, Tallmadge Township, Wright Township, East Grand Rapids, Ada Township, Gaines Township and Caledonia Township.

Rachel Watson is a Grand Rapids Business Journal staff reporter who covers food, manufacturing, small business, banking and finance, HR and diversity and sustainability. Email Rachel at rachelw at grbj dot com. Follow her on Twitter @RachelWatson86

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